This invention relates to die apparatus which includes novel means for the concentric alignment of a plurality of spaced bores or orifices in separate elements of a die assembly, and to novel configurations of certain elements of the assembly. The invention is disclosed in an embodiment intended for applying a plastic insulating layer to an electrical wire. In the art of applying an insulating layer to a conductor wire, it is common practice to pass the wire through a die apparatus while injecting molten plastic into the die cavity. During the process, it is desirable to keep the wire concentrically aligned with the die orifice to achieve a concentric and uniform insulating layer of plastic upon the wire. This is usually done by passing the wire through a die insert upstream from the die orifice where the molten plastic is applied to the wire. To achieve a properly coated wire, the die insert must be positioned such that the wire is in constant axial alignment with the die orifice.
Die apparatus to date, of which the present inventor is aware, include cylindrically shaped elements fit within one another to achieve proper positioning of the conductor passing therethrough. Since, as is generally known to those skilled in the art, only very slight tolerances are permissible in producing an insulating layer of uniform thickness required for electrical conductor wire, the cylindrical-fit approach has proven very costly to implement. Applicant has found that each of the cylindrical elements must be finely machined to the strictest of tolerances to achieve the proper fitting and alignment of the die insert within the head assembly.
A principal object of the present invention is to provide an assembly of die elements having novel and improved means for ensuring precise axial alignment of a plurality of spaced orifices in separate elements of the assembly.
Another object is to provide die elements of novel configuration for use in a die assembly wherein a layer of molten plastic is applied to an electrical conductor as the latter travels through the assembly.
A further, more specific object is to provide a die apparatus which uses tapered, as opposed to cylindrical, elements to align conductor wire with a die orifice to achieve a proper coating of an insulating layer upon the conductor wire.
It is another object of the present invention to provide a die apparatus of the cross-head type for applying an insulating layer of plastic upon a conductor in which the die insert is easily mounted for axial alignment within the cross head.
It is a further object of the present invention to provide a tapered die apparatus for applying an insulating layer to a conductor wire which is simple in design and assembly yet achieves very satisfactory results.
Other objects will in part be obvious and in part appear hereinafter.